This invention relates to a sheet folding apparatus of an image forming apparatus such as a copying machine, wherein driving force is controlled in accordance with the load increasing while a sheet folding roller in a folding mechanism folds a paper sheet having an image formed, in the case where it practices sheet folding such as folding in three (hereinafter referred to as a Z-folding).
Up to now, in a sheet folding mechanism for practicing a sheet folding process such as a Z-folding process, as disclosed in the Japanese publication Tokkaisho No. S61-248861, it has been put in practice to make twice-folding of a Z-fold type by a first-stage roller pair and a second-stage roller pair; however, because folding is not enough made by those roller pairs only, it has been put in practice that a roller for strengthening fold is pressed to one of the second-stage pair of rollers so as to secure a firm folding state certainly. This is done because the pressing force of each of the roller pairs cannot be strengthened in respect of the driving force, to make an insufficient fold line which is not acceptable for practical use, and in order to make up for it, a mechanism for strengthening a fold is added; this is not preferable because the apparatus is made larger-sized.
Further, in the Japanese publication No. Tokkaisho S61-248863, it is disclosed that, while paper sheet folding proceeds as a paper sheet is conveyed between a two rollers forming a roller pair, the folding rollers are rotated in the forward and reverse direction alternately to repeat the back-and-forth movement of a paper sheet in the path for making a fold plural times, to make a firm fold.
Further, also in the Japanese publication Tokkaisho No. S62-16987, it is disclosed that an insufficient and imperfect fold is compensated for by providing a mechanism for strengthening a fold after paper sheet folding is once finished by a pair of rollers.
However, the addition of a mechanism for strengthening a fold such as a roller for strengthening a fold, or the providing of a mechanism for practicing a repeating operation such as moving back and forth at the roller site of carrying out sheet folding, is not preferable because it makes the apparatus complicated and larger-sized by that. Further, if a repeating operation such as moving back and forth is practiced, it is produced the defect that the time required for one cycle of paper sheet folding becomes longer, which lowered the efficiency and makes the productivity worse.
Further, this invention relates to a sheet folding apparatus, wherein it is accomplished that a folding mechanism for practicing a sheet folding process such as a Z-folding process for a paper sheet having an image formed on it in an image forming apparatus such as a copying machine is simplified, a precise fold is obtained, there is posed no problem such as a paper jam, and a recovery processing can be done simply and certainly even though a paper jam occurs.
Up to now, as disclosed in the Japanese publications Jikkaisho No. S63-190254 and Tokkaihei No. H9-77360, it has been put in practice that, because a first-time folding path, a second-time folding path, and an ejecting path after twice-folding were independently and separately provided, a number of guide members such as guide plates making up a sheet conveyance path were arranged. Paper sheet paths in a sheet folding mechanism for practicing a sheet folding process such as a Z-folding process for a paper sheet having an image formed on it in an image forming apparatus such as a copying machine have had a complicated structure with paths corresponding to the respective roles formed separately in the above-mentioned way.
However, when it is posed a problem of a jam such that occurs in the folding path positioned inside among the three paper conveyance paths in the sheet folding apparatus, it is difficult to reach from the outside, and its releasing and recovery must be done by dismounting the outside conveyance paths, which takes time and is accompanied by considerable big difficulties.
Further, this invention relates to a sheet folding apparatus for practicing a sheet folding process and to an image forming apparatus provided with the sheet folding apparatus.
For a finisher of a copying machine or a printer, it is widely used an apparatus for applying a sheet folding process to a paper sheet having an image formed on it.
It is necessary that a sheet folding apparatus as such a finisher is small-sized because it is used in combination with an image forming apparatus mainframe, and on top of it, because an image forming apparatus forms an image on paper sheets of various sizes, it is required for the sheet folding apparatus to be capable of coping with various sizes of paper sheet.
In order to meet such a requirement, various kinds of sheet folding apparatus has been heretofore proposed. As regards a folding mechanism, it is mostly used such one that practices folding through giving a buckle to a paper sheet by moving it forward with its leading edge stopped and feeding the buckle portion between a pair of folding rollers, for the reason that the folding mechanism part can be made small-sized.
In such a sheet folding apparatus, for the purpose of coping with various sizes, a mechanism to displace the position of stopping member for stopping the leading edge of a paper sheet is employed.
For example, a mechanism having stopping members provided at plural positions and making these stopping members selectively come into or out of the paper conveyance path by means of a solenoid, a mechanism using a screw to displace a stopping member as shown in the Japanese publication Tokkaihei No. H10-194586, a mechanism moving a stopping member by means of a pinion and a rack, etc. have been disclosed.
However, a conventional sheet folding apparatus has been unsatisfactory because various restrictions were produced, that it became of high cost, that it was difficult to make small-sized, etc., for the reason that it must satisfy the conditions that the stopping member was capable of moving, that the whole of the apparatus was made small-sized, etc.
That is, a sheet folding apparatus using a plurality of stopping members became of high cost owing to the number of parts increasing; further, as regards one that displaces the stopping member by means of a screw, the moving velocity of the stopping member was slow owing to its being driven by a screw which made the switching of paper size take a longer time, and one using a rack and a pinion was difficult to make small-sized; each had both merits and demerits and was unsatisfactory.
It is the first object of this invention to provide a sheet folding apparatus which is made small-sized, capable of making a precise fold certainly, stabilized, and of a good efficiency by eliminating the above-mentioned disadvantage of the conventional technology.
It is the second object of this invention to provide a sheet folding apparatus having a structure that is easy to handle, simple, and hard to become out of order.
It is the third object of this invention to provide a sheet folding apparatus which can be made small-sized and is of low cost by solving the above-mentioned problems in a conventional sheet folding apparatus, in particular, in a sheet folding apparatus to be used as a finisher of an image forming apparatus, and an image forming apparatus provided with the above-mentioned sheet folding apparatus.
The first object can be accomplished by any one of the structures (1) to (5).
(1) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized by being provided with a control means for temporarily reducing the rotating speed of each of the folding rollers, at a timing when the paper sheet is gripped between the roller pair.
(2) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized by being provided with a control means for temporarily reducing the rotating speed of each of the folding rollers, by switching a speed reducing mechanism directly coupled to a motor by a clutch with the number of revolutions per minute of the motor kept constant, at a timing when the paper sheet is gripped between the roller pair.
(3) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized by being provided with a control means for temporarily increasing the drive current of a direct-current motor as a drive means for each of the folding rollers, at a timing when the paper sheet is gripped between the roller pair.
(4) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized by being provided with a control means for temporarily increasing the pulse rate of a pulse motor as a drive means for each of the folding rollers, at a timing when the paper sheet is gripped between the roller pair.
(5) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized by being provided with a control means for temporarily changing the driving electric power of a drive means for each of the folding rollers from a stationary value to another stationary value higher than that, at a timing when the paper sheet is gripped between the roller pair.
The second object can be accomplished by the following structure (6) or (7).
(6) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge hitting the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized in that, in the folding apparatus, a sheet conveyance path in a part for making up the leading edge portion of the paper sheet for the final folding of the Z-folding and a sheet ejection path for the paper sheet having been finally folded are made one and the same.
(7) A sheet folding apparatus which comprises a sheet conveyance means for conveying a paper sheet having an image formed on it and a stopping member capable of moving for adjusting its position provided in a conveyance path in order to stop a paper sheet conveyed by the sheet conveyance means at its leading edge colliding against the stopping member, and forms a fold by introducing the buckle portion of the paper sheet formed by the stopping member between a roller pair composed of two folding rollers and gripping it by the rollers, characterized in that, in the folding apparatus, there are provided a detecting means for detecting whether a paper sheet is moving forward or backward between a paper conveyance path in a part for making up the leading edge portion of the paper sheet for the final folding of the Z-folding and the roller pair by which the paper sheet is finally folded, and a control means for ejecting the paper sheet having been finally folded by retracting the stopping member in the folding path on the basis of the detection information of the detecting means.
In the above, xe2x80x9cthe leading edge portion for the final folding of the Z-foldingxe2x80x9d means the fold portion before the final one (the fold xe2x80x9cbxe2x80x9d to be described later), which becomes the leading edge portion playing a role to determine the position of the final fold (the fold xe2x80x9caxe2x80x9d to be described later) where the final folding is to be done.
The above-mentioned third object of this invention can be accomplished by any one of structures (8) to (16) described below.
(8) A sheet folding apparatus comprising a first conveyance means, a stopping member for stopping the leading edge of a paper sheet conveyed by the first conveyance means, and a second conveyance means for gripping to convey the buckle portion of a paper sheet which have been buckled by being conveyed by the first conveyance means with its leading edged stopped by the stopping member, characterized by further comprising a toothed belt for supporting the stopping member and a belt moving means for moving the toothed belt, wherein the belt moving means makes the stopping member stop at a position selected out of a plurality of specified positions.
(9) A sheet folding apparatus as set forth in the above-mentioned structure (8), characterized in that the toothed belt is made up of an endless belt.
(10) A sheet folding apparatus as set forth in the above-mentioned structure (8) or (9), characterized in that the belt moving means is made up of a stepping motor.
(11) A sheet folding apparatus as set forth in any one of the above-mentioned structures (8) to (10), characterized by further comprising two sheet folding portions each comprising the aforesaid stopping member, the aforesaid toothed belt, and the aforesaid belt moving means.
(12) A sheet folding apparatus as set forth in any one of the above-mentioned structures (8) to (11), characterized in that the aforesaid belt moving means moves the aforesaid stopping member to a retraction position.
(13) An image forming apparatus characterized by comprising a first finisher having a sheet folding apparatus as set forth in any one of the above-mentioned structures (8) to (12) and an image forming section for forming an image on a paper sheet and conveying the paper sheet to the first finisher.
(14) An image forming apparatus as set forth in the above-mentioned structure (13), characterized by further comprising a second finisher, wherein a paper sheet having been conveyed from the aforesaid first finisher is processed in the second finisher.
(15) An image forming apparatus as set forth in the above-mentioned structure (13) or (14), characterized in that the aforesaid first finisher comprises a punching means.
(16) An image forming apparatus as set forth in the above-mentioned structure (14) or (15), characterized in that the aforesaid second finisher comprises a stapler.